The present invention is generally related to recording systems for digital video and other data, and in particular, provides methods and structures for preventing the read/write head from moving too close to the center of a recording disk.
Video Cassette Recorders ("VCRs") dominate the consumer video market, due in part to their combination of low cost and recording capabilities. VCR analog magnetic tape recording cassettes can be used to record, play-back, and store video images in a format which is well adapted for use with existing analog television signals. The ability to record allows consumers to use the standard VHS VCR to save television shows and home movies, as well as for play-back of feature films.
The structure of VCR systems and recording media are adapted to record and archive existing television signals. Specifically, a large amount of analog data is presented on a standard television screen during a standard length feature film. VCR systems record this analog data using analog tape recording media. The VCR tape cassettes can be removed from the recording/play-back equipment for storage, thereby minimizing the system costs when large numbers of movies are stored.
While VCR systems successfully provide recording and archive capabilities at low cost, these existing consumer video systems have significant disadvantages. For example, accessing selected portions of a movie stored on a VCR tape can be quite slow. In particular, the cassette must be rewound to the beginning of the movie between each showing, which can involve a considerable delay. Additionally, transferring data to and from the tape takes a substantial amount of time. There has been little incentive to provide high speed accessing and transfer of the video data, as movies are typically recorded and played by the consumer in real time. Alternatives providing faster access are commercially available (for example, optical video disks), but these alternatives generally have not been able to overcome the VCR's low cost and recording capabilities.
Recent developments in video technology may decrease the VCR's advantages over alternative systems. Specifically, standard protocols have recently been established for High Definition TeleVision ("HDTV"). Although digital video cassette tapes are already available, the amount of data presented in a single HDTV feature film using some of the new protocols will represent a substantial increase over existing digital VCR system capacities. Optical disks may be able to accommodate these larger quantities of digital data. Unfortunately, despite many years of development, a successful low cost optical recording system has remained an elusive goal.
Personal computer magnetic data storage systems have evolved with structures which are quite different than consumer video storage systems. Modern personal computers often include a rigid magnetic disk which is fixed in an associated disk drive. These hard disk drive systems are adapted to access and transfer data to and from the recording surface at high rates. It is generally advantageous to increase the total data storage capacity of each hard disk, as the disks themselves are typically fixed in the drive system. Hence, much of the data that is commonly used by the computer is stored on a single disk.
The simplicity provided by a fixed disk drive system helps maintain overall system reliability, and also helps reduce the overall storage system costs. Nonetheless, removable hard disk cartridge systems have recently become commercially available, and are now gaining some acceptance. While considerable quantities of computer data can be stored using these removable hard disk cartridge systems, their complexity, less than ideal reliability, and cost has limited their use to selected numbers of high-end personal computer users.
One particular disadvantage of known removable disk drive systems is the complexity of their structure. For example, existing removable hard disk drives generally support a data transfer head on a movable arm to selectively position the head along a recording surface of the disk. To allow the disk to rotate, and to allow the head to translate over the rotating disk, the spindle drive for the disk and the arm support structure must be aligned quite accurately. Additionally, known removable hard disk drives often include a fixed "inner crash stop", a structure which limits radial inward movement of the head to prevent the head from moving inward beyond the recording surface and against the disk hub. This accurately positioned fixed limit structure may include an elastomeric material to help resiliently redirect the arm onto the recording surface. Unfortunately, the housing base on which all of these tight tolerance components are assembled are generally machined, and each additional component adds to the fabrication costs, as well as the complexity of the assembly.
In light of the above, it would be desirable to provide improved systems, devices, and methods for storing digital video and other data. It would be particularly desirable if these improvements were adapted for digital video data such as the new HDTV protocols, and had the ability to record, archive, access, and transfer digital feature films at high speeds, with good reliability, and at a low system cost, thereby expanding the benefits from the tremendous economies of scale from the consumer video market.